Git.pm: Handle failed commands' output
Currently if an external command returns error exit code, a generic exception is thrown and there is no chance for the caller to retrieve the command's output. This patch introduces a Git::Error::Command exception class which is thrown in this case and contains both the error code and the captured command output. You can use the new git_cmd_try statement to fatally catch the exception while producing a user-friendly message. It also adds command_close_pipe() for easier checking of exit status of a command we have just a pipe handle of. It has partial forward dependency on the next patch, but basically only in the area of documentation. Signed-off-by: Petr Baudis <pasky@suse.cz> Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Petr Baudis
Junio C Hamano
parent
97b16c0674
commit
8b9150e3e3
@ -7,6 +7,7 @@
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use strict;
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use Git;
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use Error qw(:try);
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my $repo = Git->repository();
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@ -31,7 +32,17 @@ sub andjoin {
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}
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sub repoconfig {
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my ($val) = $repo->command_oneline('repo-config', '--get', 'merge.summary');
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my $val;
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try {
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$val = $repo->command_oneline('repo-config', '--get', 'merge.summary');
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} catch Git::Error::Command with {
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my ($E) = shift;
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if ($E->value() == 1) {
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return undef;
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} else {
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throw $E;
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}
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};
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return $val;
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}
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192
perl/Git.pm
192
perl/Git.pm
@ -24,16 +24,17 @@ $VERSION = '0.01';
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my $version = Git::command_oneline('version');
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Git::command_noisy('update-server-info');
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git_cmd_try { Git::command_noisy('update-server-info') }
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'%s failed w/ code %d';
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my $repo = Git->repository (Directory => '/srv/git/cogito.git');
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my @revs = $repo->command('rev-list', '--since=last monday', '--all');
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my $fh = $repo->command_pipe('rev-list', '--since=last monday', '--all');
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my ($fh, $c) = $repo->command_pipe('rev-list', '--since=last monday', '--all');
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my $lastrev = <$fh>; chomp $lastrev;
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close $fh; # You may want to test rev-list exit status here
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$repo->command_close_pipe($fh, $c);
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my $lastrev = $repo->command_oneline('rev-list', '--all');
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@ -44,11 +45,11 @@ require Exporter;
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@ISA = qw(Exporter);
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@EXPORT = qw();
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@EXPORT = qw(git_cmd_try);
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# Methods which can be called as standalone functions as well:
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@EXPORT_OK = qw(command command_oneline command_pipe command_noisy
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version exec_path hash_object);
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version exec_path hash_object git_cmd_try);
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=head1 DESCRIPTION
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@ -88,7 +89,7 @@ increate nonwithstanding).
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=cut
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use Carp qw(carp); # croak is bad - throw instead
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use Carp qw(carp croak); # but croak is bad - throw instead
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use Error qw(:try);
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require XSLoader;
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@ -193,21 +194,35 @@ In both cases, the command's stdin and stderr are the same as the caller's.
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=cut
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sub command {
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my $fh = command_pipe(@_);
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my ($fh, $ctx) = command_pipe(@_);
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if (not defined wantarray) {
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_cmd_close($fh);
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# Nothing to pepper the possible exception with.
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_cmd_close($fh, $ctx);
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} elsif (not wantarray) {
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local $/;
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my $text = <$fh>;
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_cmd_close($fh);
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try {
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_cmd_close($fh, $ctx);
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} catch Git::Error::Command with {
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# Pepper with the output:
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my $E = shift;
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$E->{'-outputref'} = \$text;
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throw $E;
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};
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return $text;
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} else {
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my @lines = <$fh>;
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_cmd_close($fh);
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chomp @lines;
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try {
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_cmd_close($fh, $ctx);
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} catch Git::Error::Command with {
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my $E = shift;
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$E->{'-outputref'} = \@lines;
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throw $E;
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};
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return @lines;
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}
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}
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@ -222,12 +237,18 @@ of the command's standard output.
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=cut
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sub command_oneline {
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my $fh = command_pipe(@_);
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my ($fh, $ctx) = command_pipe(@_);
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my $line = <$fh>;
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_cmd_close($fh);
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chomp $line;
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try {
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_cmd_close($fh, $ctx);
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} catch Git::Error::Command with {
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# Pepper with the output:
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my $E = shift;
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$E->{'-outputref'} = \$line;
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throw $E;
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};
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return $line;
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}
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@ -251,7 +272,32 @@ sub command_pipe {
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} elsif ($pid == 0) {
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_cmd_exec($self, $cmd, @args);
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}
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return $fh;
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return wantarray ? ($fh, join(' ', $cmd, @args)) : $fh;
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}
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=item command_close_pipe ( PIPE [, CTX ] )
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Close the C<PIPE> as returned from C<command_pipe()>, checking
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whether the command finished successfuly. The optional C<CTX> argument
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is required if you want to see the command name in the error message,
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and it is the second value returned by C<command_pipe()> when
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called in array context. The call idiom is:
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my ($fh, $ctx) = $r->command_pipe('status');
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while (<$fh>) { ... }
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$r->command_close_pipe($fh, $ctx);
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Note that you should not rely on whatever actually is in C<CTX>;
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currently it is simply the command name but in future the context might
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have more complicated structure.
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=cut
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sub command_close_pipe {
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my ($self, $fh, $ctx) = _maybe_self(@_);
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$ctx ||= '<unknown>';
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_cmd_close($fh, $ctx);
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}
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@ -280,9 +326,8 @@ sub command_noisy {
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} elsif ($pid == 0) {
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_cmd_exec($self, $cmd, @args);
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}
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if (waitpid($pid, 0) > 0 and $? != 0) {
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# This is the best candidate for a custom exception class.
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throw Error::Simple("exit status: $?");
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if (waitpid($pid, 0) > 0 and $?>>8 != 0) {
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throw Git::Error::Command(join(' ', $cmd, @args), $? >> 8);
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}
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}
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@ -340,12 +385,117 @@ are involved.
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# Implemented in Git.xs.
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=back
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=head1 ERROR HANDLING
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All functions are supposed to throw Perl exceptions in case of errors.
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See L<Error>.
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See the L<Error> module on how to catch those. Most exceptions are mere
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L<Error::Simple> instances.
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However, the C<command()>, C<command_oneline()> and C<command_noisy()>
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functions suite can throw C<Git::Error::Command> exceptions as well: those are
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thrown when the external command returns an error code and contain the error
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code as well as access to the captured command's output. The exception class
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provides the usual C<stringify> and C<value> (command's exit code) methods and
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in addition also a C<cmd_output> method that returns either an array or a
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string with the captured command output (depending on the original function
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call context; C<command_noisy()> returns C<undef>) and $<cmdline> which
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returns the command and its arguments (but without proper quoting).
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Note that the C<command_pipe()> function cannot throw this exception since
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it has no idea whether the command failed or not. You will only find out
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at the time you C<close> the pipe; if you want to have that automated,
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use C<command_close_pipe()>, which can throw the exception.
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=cut
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{
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package Git::Error::Command;
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@Git::Error::Command::ISA = qw(Error);
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sub new {
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my $self = shift;
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my $cmdline = '' . shift;
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my $value = 0 + shift;
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my $outputref = shift;
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my(@args) = ();
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local $Error::Depth = $Error::Depth + 1;
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push(@args, '-cmdline', $cmdline);
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push(@args, '-value', $value);
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push(@args, '-outputref', $outputref);
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$self->SUPER::new(-text => 'command returned error', @args);
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}
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sub stringify {
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my $self = shift;
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my $text = $self->SUPER::stringify;
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$self->cmdline() . ': ' . $text . ': ' . $self->value() . "\n";
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}
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sub cmdline {
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my $self = shift;
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$self->{'-cmdline'};
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}
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sub cmd_output {
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my $self = shift;
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my $ref = $self->{'-outputref'};
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defined $ref or undef;
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if (ref $ref eq 'ARRAY') {
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return @$ref;
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} else { # SCALAR
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return $$ref;
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}
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}
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}
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=over 4
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=item git_cmd_try { CODE } ERRMSG
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This magical statement will automatically catch any C<Git::Error::Command>
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exceptions thrown by C<CODE> and make your program die with C<ERRMSG>
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on its lips; the message will have %s substituted for the command line
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and %d for the exit status. This statement is useful mostly for producing
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more user-friendly error messages.
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In case of no exception caught the statement returns C<CODE>'s return value.
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Note that this is the only auto-exported function.
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=cut
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sub git_cmd_try(&$) {
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my ($code, $errmsg) = @_;
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my @result;
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my $err;
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my $array = wantarray;
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try {
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if ($array) {
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@result = &$code;
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} else {
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$result[0] = &$code;
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}
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} catch Git::Error::Command with {
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my $E = shift;
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$err = $errmsg;
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$err =~ s/\%s/$E->cmdline()/ge;
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$err =~ s/\%d/$E->value()/ge;
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# We can't croak here since Error.pm would mangle
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# that to Error::Simple.
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};
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$err and croak $err;
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return $array ? @result : $result[0];
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}
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=back
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=head1 COPYRIGHT
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@ -384,14 +534,14 @@ sub _cmd_exec {
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# Close pipe to a subprocess.
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sub _cmd_close {
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my ($fh) = @_;
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my ($fh, $ctx) = @_;
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if (not close $fh) {
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if ($!) {
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# It's just close, no point in fatalities
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carp "error closing pipe: $!";
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} elsif ($? >> 8) {
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# This is the best candidate for a custom exception class.
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throw Error::Simple("exit status: ".($? >> 8));
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# The caller should pepper this.
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throw Git::Error::Command($ctx, $? >> 8);
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}
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# else we might e.g. closed a live stream; the command
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# dying of SIGPIPE would drive us here.
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